What do you think is the difference between a JRPG and one from the West? I think JRPGs have these giant worlds where the story has your head going in circles to try and make sense of it all. Western RPG's seem able to compress everything into bite-sized piece and still make everything make sense.
Gameplay-wise, JRPG's seem to focus on just adjusting your gear and what abilities you use; like the Matera system from FFVII. Western RPGs seem to take a more sophisticated approach, where you not only select your gear and abilities, but also how you use them. Also, JRPGs start off with the world around you being really limited, where all you have to do is get one place to the next before it finall opens up and you are free to explore. Western RPGs on the other hand have the whole world open to you from the start, so you can start a story quest in one place, then take your time with sidequests and exploration before moving on with the story (Elder Scrolls?).
I'm not sure if what I've written makes sense, but feel free to comment if you can understand it.